1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device with a triple-well structure.
2. Description of the Prior Art
Typically, more serious influence by defect and impurities is given as integration of a semiconductor device increases. Lattice defects and impurities which exist in the active area of a semiconductor device reduce life time of the minority carrier and increase leakage current rapidly. Also, such lattice defects and impurities deteriorate film quality of the oxide film and make the threshold voltage of a CMOS device disuniform. Thus, technology to remove lattice defects and impurities is needed. The following two(2) methods are used at present.
The first method is to use the heat process of three(3) steps to execute heat treatment respectively at high, low and high temperature. The second method is to form a lattice defect layer on a semiconductor substrate by heat treatment or ion implantation using high energy after damaging the backside of the semiconductor substrate. One of the disadvantages of the second method is to need long-time process at high temperature, and its process is complex. Particularly, it is a problem in that the second method removes dislocation to act as a trap site of impurities because of process heat, and impurities return to the active area of the semiconductor substrate again.
On the other hand, the conventional method to remove defects and impurities by ion implantation using million electron volts(MeV) is known as the technology to remove defects in a device by inducing defect-to-defect interaction after forming defects deeply in the semiconductor substrate by ion implantation of dopants such as silicon(Si) and carbon(C) that have a little influence on electric property of a parent material.